Monolithic RC oscillators are increasingly becoming the preferred clock source in many applications, which typically have used bulky crystal or MEMS oscillators. Using novel methods to compensate for the frequency inaccuracy caused by the temperature coefficient (TC) of the resistors used in the reference RC networks, prior works have achieved excellent short-term frequency stability , . While this level of performance undoubtedly makes RC oscillators a desirable option even in applications requiring medium-to-high stability clock sources, they cannot be deployed commercially until the performance is guaranteed over their lifetime. Unfortunately, literature on the aging behavior of RC oscillators is scarce. Given this critical shortcoming, this paper quantifies aging in RC oscillators and presents methods to overcome it. The results obtained from prototype oscillators indicate that aging can cause more than 5000ppm long-term frequency drift. The proposed compensation techniques reduce it to less than 500ppm.